Interpretive Summary: The pear psylla is one of the most serious insect pests of European pear varieties. Infestation causes decreased fruit size and quality, defoliation, reduced winter hardiness, and fruit bud development. The insect also is the vector for the disease known as pear decline. Twenty pear cultivars and breeders’ selections derived from crosses between the Asian pear species, Pyrus ussuriensis or Pyrus pyrifolia, with the European pear, Pyrus communis, were evaluated for resistance to pear psylla using an assay which measured inhibition of feeding by the larvae. Two P. ussuriensis × P. communis hybrid selections (NY 10355 and NY 10359) and the P. communis landrace cultivars, ‘Batjarka’ and 'Zelinka’, were the most resistant to nymphal feeding. These selections and cultivars should be valuable parents for the breeding of new pear cultivars with resistance to pear psylla.

Technical Abstract:
Twenty-one pear cultivars and breeders’ selections with interspecific pedigrees involving Pyrus ussuriensis Max. or P. pyrifolia (Burm.) Nakai crossed with P. communis were assessed to resistance pear psylla (Cacopsylla pyricola Förster) using a nymphal feeding antixenosis assay. The proportion of nymphs live and present on the plants varied from 0.52 for Purdue 77-73, a P. ussuriensis × P. communis hybrid, to 0.08 for ‘Zelinka’, a P. communis cultivar from Eastern Europe. Two P. ussuriensis × P. communis hybrid selections (NY 10355 and NY 10359) and the P. communis landrace cultivars, ‘Batjarka’ and Zelinka’, were the most resistant to nymphal feeding. The most resistant germplasm should be valuable genetic resources for the breeding of new pear cultivars with resistance to pear psylla.